How much lime should I add to my compost bin?

Tony Hutchinson, by email

Stefan says: You should not need to add any, although in many older gardening books, and some new ones, you’ll see the recipe for making good compost includes a recommendation that lime be dusted over the compost several times during each filling. The justification is to reduce acidity in the bin.

What puzzles me is why compost should ever be acidic enough to justify being limed. In all my many years of compost making, I’ve never added lime to the bin, and by carefully testing the pH, have proven to myself it was never necessary.